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Thread: Stouffer's 4x5 step wedge for exposing negative?

  1. #11
    mandoman7's Avatar
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    Re: Stouffer's 4x5 step wedge for exposing negative?

    Its desirable IMO with calibration tests to replicate actual shooting conditions to eliminate variables. With bellows extensions, filters, incandescent light, etc., there are some variables that are getting introduced that could effect results.

    After testing for awhile, I found that I was really only using zone I, V, and VIII readings to determine the spread that my dev time was giving. So my tests evolved to a method based on Hutching's described in the back of his pyro book. Using a board with a strong light at one end that graduates through a full 10 zones, you can mark the points where my meter reads I, II, and VIII, The advantage is that I'm using my regular spot meter and a normal lens with a reliable shutter speed.
    John Youngblood
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  2. #12
    jvuokko's Avatar
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    Re: Stouffer's 4x5 step wedge for exposing negative?

    mandoman7, thanks! That is new method to me. Never heard before.
    I have used combination of three cards with Q&D roll film calibration. One is graycard, one is almost black and one is white at VIII, all with black velvet background. Photographed on single negative with normal lenses etc.

    ic_racer, sensitometer would be really nice. There's lot of them usually at ebay, but problem is that they need 110v/60Hz current and where I live, it's 220v/50Hz.
    If they're not sensitive for current's frequency then transformers are easy to found and relative cheap, but if frequency should also converted from 50Hz to 60Hz, then it is a problem.
    (same problem prevents me using GraLab's timers etc).
    Jukka Vuokko
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  3. #13

    Re: Stouffer's 4x5 step wedge for exposing negative?

    buy a ZoneMaster enlarging exposure meter, it also can be used as a densitometer under enlarger, it uses AAA battery, no current problem.

  4. #14

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    Re: Stouffer's 4x5 step wedge for exposing negative?

    Quote Originally Posted by jvuokko View Post
    Hi,

    this is a bit dumb question, but how do you manage to put 4x5 step tablet with a film on the film holder (sandwitch -style)? This is the most common style that I have seen and is taught by books (except BTZS).


    What's your method?

    Thanks,
    Jukka

    I adjust the height of the enlarger to illuminate an area about 8X10" in size and contact print the step wedge to a sheet of film in the middle of this area. I use a small contact printing frame for this, but you could, 1) just place a piece of glass over the sandwich, or 2) place the step wedge over the film in a film holder. .

    For BTZS testing I now use a sensitometer but when I did this type of testing with an enlarger I used a Metrolux timer (which measures by light integration) to ensure accurate exposure times.

    If you use an enlarger with a tungsten type light I would suggest adding an 80A filter to balance for daylight.

    Sandy King

  5. #15
    Nicholas O. Lindan
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    Re: Stouffer's 4x5 step wedge for exposing negative?

    Thinking about the light color ... it shouldn't make any difference in step tablet testing.

    All the grains in the film have the same spectral sensitivity - the contrast of the film will not (or should not) change with the color of light.

    Of course the relationship of an exposure meter reading to the resulting film density will change with light color - but if using an enlarger that's not much of an issue as the light used for the exposure is arbitrary - i.e. whatever it is that works.

    The results of the step tablet test with an enlarger will be the HD curve of the film. The light meter EI setting won't be determined by this test unless you have a film-plane light meter like a Sinar, in which case the 80A filter would be a help in finding the right EI setting for photographs taken with natural light.

    It is possible to find the relation between an enlarging meter reading and f-stop timer setting - the Darkroom Automation meter comes to mind, for some reason - and a corresponding light meter EV reading/aperature/ASA/shutter speed. However, unless a lot of film testing is planned this may be too much effort.

    FWIW: with the DA settings, a total exposure of 7.0 stops [meter reading + timer setting] works well for contacting a step tablet on to TMX-100 film. That's about 3 stops less exposure than what will produce max black on MGIV RC with a grade #2 filter - where the film is exposed without the filter. The film will just rise above B+F on step 30 of a 31-step tablet.

  6. #16
    jvuokko's Avatar
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    Re: Stouffer's 4x5 step wedge for exposing negative?

    Salihomba, thanks for the tip!


    About the using 80A. It's a good idea, because it simulates "general" daylight. Especially with orthochromatic or orthopanchromatic it could make difference. At least I would imagine so.

    But... after taking reading measurements of my enlarger, with f/11 it gives EV4 for ISO 100 when lowered to 22,5cm (about 8.8 inches). So it's already a quite low. Get only about twice a size of 4x5 sheet of lighted area (about 8x10).

    So if I add 80A, then I am out of light, especially because orthopanchromatic and otrhopan materials tend to be slow..

    Measurement is taken with spot meter from bright white card.

    Often I have seen tip to use light meter with cell pointed towards the enlarger lens (and thus the light source), but it doesn't seem reasonable. With incident meter it would be ok, but... Because the light comes from only above, it gives way lower reading than reflective readings from white card.
    Perhaps reading thru step wedge's middle density towards the light would work..

    But I doubt that it would give any help to my unpowered enlarger.
    Jukka Vuokko
    Flickr

  7. #17

    Re: Stouffer's 4x5 step wedge for exposing negative?

    A step wedge slide for testing.

    camera with 210mm lens focus on infinity and then put it close to acryic plate by the window, then treat plate as Zone X, meter and shoot.

  8. #18
    jvuokko's Avatar
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    Re: Stouffer's 4x5 step wedge for exposing negative?

    Okay, it really seems that the enlarger is not the best option (but it would allow the testing of 120 and 135 material easily).
    Why I don't like enlarger?

    Color temperature issues - my enlarger has an halogen light source, so I guess that it's somewhat close of 3400K or normal 'tungsten'. But despite of 100W power, it does not give enought light for BTZS's 'standarsized EV4/ISO100/f11'. Perhaps the diffusion chamber is just too much. Condenser enlarger would give more light (I have old Meopta Opemus 4 at the cellar, perhaps it would do the trick!)

    Use a 80A with this candle? No way...

    It takes ~0.25 sec until the maximum brightness is reached, so exposure times shorter than one second suffers badly. Is the halogen slower than normal tungsten bulb?

    It is good that I actually measured the time that enlarger needs until the light is fully lit up. I have used short times often and sometimes wondered why my calculations don't match when I change aperture/time combination. I really thought that it would took less than 0.1 second to get light on..
    Jukka Vuokko
    Flickr

  9. #19
    Nicholas O. Lindan
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    Re: Stouffer's 4x5 step wedge for exposing negative?

    Quote Originally Posted by jvuokko View Post
    I really thought that it would took less than 0.1 second to get light on..
    A standard PH212 enlarging bulb requires a 50 mSec adjustment for the turn on delay and the turn off afterglow of the bulb.

    A test for determining the effective adjustment time you need to compensate for the lamp delays is described in an application note on the Darkroom Automation web site: http://www.darkroomautomation.com/su...2LampDelay.pdf.

    Claimer: I am associated with Darkroom Automation and I do have a vested interest...but I'm also a satisfied customer.

  10. #20

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    Re: Stouffer's 4x5 step wedge for exposing negative?

    I would use the BTZS method on the baseboard of your enlarger. I made a simple jig with a right angle of film scraps taped to a piece of black matboard so that I can slide the sandwich of step wedge/film into the right angle on which I place a sheet of glass and then expose.

    A couple of questions that I can't remember off the top of my head:
    • Is the recommended EV reading off the baseboard 4?
    • I have used the white light from a dichro head in the past. Now I have a cold light. Will that make any difference to future testing?

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